\documentclass{ctexart}
\usepackage{avanti}
\everymath{\color{Solarized-magenta}}
\pagestyle{empty} % 没有页眉和页脚

 % define the plot style and the axis style
\tikzset{base/.style={smooth,thick,Solarized-base01}}
\tikzset{arrow/.style={->,>=stealth,base}}

\begin{document}

\begin{figure}[!ht]
    \centering
    \begin{tikzpicture}

        \draw [arrow] (0,0) -- (8.5,0);
        \draw [arrow] (0,0) -- (0,5.6);

        \draw [base,Solarized-blue,domain=0.5:6.5] plot(\x,{0.08*(\x-6.8)^2+0.7});
        \draw [base,Solarized-red,domain=0.5:6.5] plot(\x,{0.3*(\x-3.5)^2+2.5});

        \path (7.4, 0.7) node[Solarized-blue] () {经验风险};

        \path (7.4, 5.2) node[Solarized-red] () {泛化风险};

        \path (7.0, -0.3) node[Solarized-base01] () {假设空间复杂度};

    \end{tikzpicture}
\end{figure}


\end{document}